60 ELEMENTARY PHYSIOLOGY. 



on the walls of the chest; it may be easily felt at 

 several other points quite remote from the heart 

 itself, as, for instance, at the temples or at the wrists. 

 These impulses, as felt at these places, are called 

 the pulse. This index to the rate of the heart's 

 action is very convenient to the physician, since it 

 makes known to him at once any acceleration, retard- 

 ation or irregularity of the blood's circulation. 



Health of the s ^ ea dy an( ^ thorough work of the 



circulatory organs of the circulatory system -is 

 very essential to life and health. Any 

 cause which tends seriously to increase or diminish 

 the normal rate of the heart's action is a thing to be 

 avoided. The ordinary quickening of the flow of 

 the blood, as in moderate exercise of the body, is 

 not only harmless, but healthful. Here, again, exer- 

 cise must be commended as a prime condition of 

 a healthy circulation. Any part of the body which, 

 from any cause whatever, remains comparatively 

 unused, will not be supplied by the circulatory sys- 

 tem with a sufficient quantity of pure blood to main- 

 tain its vigor. Such a part will therefore gradually 

 wither and die. It follows that we need that kind 

 of exercise regularly which will call into use all 

 parts of the body, and thus prompt the flow of blood 

 into every nook and corner of our physical structure. 



OUTLINE. 



THE CIRCULATORY SYSTEM. 

 ( Central organ, the heart. 

 } Arteries, blood-vessels leading from the heart. 



